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tions. However, they responded very differently, holding up quite well 

 in storage the first year and deteriorating very rapidly the second year. 



Pressure tests of the fruits at removal from storage in the first 

 season were a good index of their subsequent shelf life. The firmer the 

 fruits, the better they kept following storage. In the second season, 

 however, firmness was very misleading. The fruits softened rapidly dur- 

 ing storage, and the higher the temperature, the more rapidly they 

 softened. Controlled atmosphere did not prevent this softening, and 

 after 70-90 days of storage, CA fruits were significantly softer than 

 ones from 32° F regular storage. Using firmness as a guide, we would 

 conclude that CA had produced poorer fruits than regular storage after 

 these storage intervals, and that the CA fruits would deteriorate more 

 rapidly following storage than those from regular storage. 



Such was not the case; the CA fruits held up better following stor- 

 age than those from regular storage. They maintained a greener ground 

 color and developed less internal breakdown than ones from regular stor- 

 age. Furthermore, they developed no scald or brown core, whereas those 

 from regular storage developed both disorders. As an index of post- 

 storage shelf life, pressure tests were very misleading in comparing CA 

 and air storages in this second year; thus, they cannot be relied upon 

 as a predictive index. 



In discussing pressure testing, mention should be made of a fairly 

 recent innovation, the so-called Mechanical Thumb. This is a device 

 which may be attached to a regular pressure tester and permits pressure 

 testing without destroying the fruit. With the Mechanical Thumb, read- 

 ings are made without removing the peel and they result in only a small 

 bruise on the apple. 



The Mechanical Thumb was developed primarily for use by inspectors, 

 so that an adequate number of fruits might be sampled without destroying 

 packed fruit. However, some interest has developed in its utility for 

 other purposes. In a recent study CPi^oc • Amer. Soc. Hort. Sci . 87:100- 

 103), Dr. G. E. Mattus of the Virginia Polytechnic Institute compared 

 the use of a Mechanical Thumb with that of a regular pressure tester on 

 over 1,3 00 lots of apples of 5 different varieties. He found that read- 

 ings with the Mechanical Thumb were subject to influence by more vari- 

 ables than those taken with the pressure tester, and therefore were less 

 reliable. It seems, then, that except in unusual circumstances where 

 destruction of the fruit is a serious deterrent to taking adequate read- 

 ings, the regular Magness -Taylor pressure tester is a more reliable tool 

 than the Mechanical Thumb. 



The results of our tests have shown that the reliability of pressure 

 tests depends upon what they are used for. As an index of fruit quality, 

 pressure differences were closely related to texture differences. As an 

 index of maturity, pressure tests were useful. But used as a prediction 

 of storage life or shelf life, pressure tests were sometimes grossly 

 misleading. 



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